The present invention relates to a grommet which is mounted in an electric wire passing portion of a panel such as a body of a vehicle in order to preserve waterproofness of an electric wire at the electric wire passing portion while protecting an electric wire which passes through the grummet.
This type of grommet is formed of a flexible material such as rubber and is fitted in a through hole (a panel hole) formed in a panel of a vehicle or the like to hold therein a wiring harness, having functions to protect the wiring harness and to preserve waterproofness at the through hole.
FIG. 5 is a sectional view which shows an example of a grommet according to the related art. For example, JP-A-4-249817 discloses a grommet similar to the above type of grommet.
The entirety of this grommet 1 is formed into an integral unit of a flexible material such as rubber. The grommet 1 includes a panel fitting portion 10 having an outer circumference on which an inner circumferential edge of a through hole Pa of a panel P is fitted, an electric wire fitting portion 30 which fits on an outer circumference of an electric wire (a wiring harness) W which passes through the through hole Pa in the panel P, and a hollow conical connecting portion 20 which connects between the panel fitting portion 10 and the electric wire fitting portion 30. The panel fitting portion 10 has a large-diameter and thick annular form. The electric wire fitting portion 30 has a small-diameter and thin cylindrical form.
The panel fitting portion 10 includes an annular flange portion 11 which is provided on an opposite side thereof to the connecting portion 20 which is larger in diameter than the through hole Pa in the panel P and is thick, an annular raised portion 13 climbing up and down at a moderate angle in section which is provided on an outer circumference of a side thereof which lies to the connecting portion 20 in such a manner as to protrude therefrom with an annular recessed portion 14 interposed between the annular flange portion 11 and itself, and a seal projection 12 provided on a side of the annular flange portion 11 which lies to the connecting portion 20 in such a manner as to protrude therefrom towards the annular raised portion 13, so as to be brought into press contact with a surface of the panel P at a distal end thereof to push the panel P towards the connecting portion 20, whereby a circumferential edge portion of the through hole Pa in the panel P which passes over the annular raised portion 13 from an opposite side to be fitted in the annular recessed portion 14 is brought into press contact with a shoulder portion of the annular raised portion 13, so that a sealing performance is secured between the panel P and the grommet by two press contact portions (sealed portions) S1, S2 which are attained in this configuration. In the illustrated example, the seal projection 12 is provided on the annular flange portion 11 further radially inwards than an outermost circumference thereof via a difference in level 15 therebetween.
Here, the annular raised portion 13 is formed as a raised portion which climbs up and down at a moderate angle, whereby the annular raised portion 13 is allowed to easily pass into the through hole Pa in the panel P when the grommet 1 is attempted to be fitted into the through hole P from the connecting portion 20 side thereof. Namely, the facilitation of fitting work of the grommet 1 is realized by forming the annular raised portion 13 into the shape which does not project largely to the outer circumference side with a difference in level.
In addition, on the surface of the panel P, since the distal end of the annular seal projection 12 is elastically pressed against the surface of the panel P, it becomes possible to easily adapt to some change in thickness of the panel P and a slight deformation of the panel P even if such change and deformation actually happen, as long as the change and deformation of the panel P fall within a permissible range of elastic deformation of the seal projection 12.
Incidentally, when applying the grommet 1 to a vehicle, a case is considered to occur when washing the vehicle, for example, in which a flow of water injected under high pressure from a high-pressure washing machine directly strikes the grommet 1. A person who is washing the vehicle has no idea on an angle at which the flow of high pressure injected water hits the grommet 1 during washing, and therefore, it is extremely important that the sealing performance of the grommet 1 is not damaged even in the event that the flow of high pressure injected water directly hits the grommet 1 at a special angle.
In the case of the grommet 1 shown in FIG. 5, however, it has been found that the maintenance of sealing property of the grommet 1 cannot be perfect depending on the angle at which the flow of high pressure injected water hits the grommet 1 due to the following reasons which can be raised as structural features of the grommet 1. First, the annular seal projection 12 is configured so as to be relatively flexible in order to cope with a change in thickness of the panel P. Second, the inner circumferential edge of the through hole Pa in the panel P is pressed against the shoulder portion of the annular raised portion 13 climbing up and down at the moderate angle in section by virtue of the pressure of the seal projection 12.
Namely, as shown in FIG. 6, in the event that a flow of high pressure injected water 101 from a high pressure washing machine nozzle 100 directly hits the seal projection 12 from the outer circumferential side to thereby deflect the seal projection 12 through an angle θ or larger, the contact pressure at the sealed portions (the press contact portions S1, S2) is lowered, leading to a risk that a gap may be produced at the relevant portions, so as to allow the injected water to intrude into the body as indicated by an arrow F.
In addition, as shown in FIG. 7, the flow of high pressure injected water 101 which has hit the panel P and rebounded hits the portion of the annular flange portion 11 which the difference in level 15 is produced, whereby the annular flange portion 11 is caused to deflect through an angle θ or larger, and the contact pressure of the seal projection 12 against the panel P is lowered. As a result, there may be caused a risk that the injected water is allowed to intrude into the body from the sealed portions (the press contact portions S1, S2) as indicated by an arrow F.